Browsing by Author "Panji, Sumir"

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    The African Coelecanth genome provides insights into tetrapod evolution
    (Macmillan Publishers, 2013) Christoffels, Alan; Hesse, Uljana; Gamieldien, Junaid; Panji, Sumir; Picone, Barbara; Van Heusden, Peter
    The discovery of a living coelacanth specimen in 1938 was remarkable, as this lineage of lobe-finned fish was thought to have become extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae. Through a phylogenomic analysis, we conclude that the lungfish, and not the coelacanth, is the closest living relative of tetrapods. Coelacanth protein-coding genes are significantly more slowly evolving than those of tetrapods, unlike other genomic features. Analyses of changes in genes and regulatory elements during the vertebrate adaptation to land highlight genes involved in immunity, nitrogen excretion and the development of fins, tail, ear, eye, brain and olfaction. Functional assays of enhancers involved in the fin-to-limb transition and in the emergence of extra-embryonic tissues show the importance of the coelacanth genome as a blueprint for understanding tetrapod evolution.
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    Ancient Genes in Cancer Gene Expression?
    (University of the Western Cape, 2004) Panji, Sumir; Hide, Winston
    Backsround: The Cancer/testis (CT) antigens are a division of germ cell specific genes not expressed in somatic cells, exceptions being placental cells and 20Vo - 4OVo of cancer types. The aptitude of CT antigens to elicit humoral immune responses, their restricted expression profile, absence of major histocompatability complex expression in male germline cells have contributed to the emergent attraction of CT antigens as ideal, prospective cancer vaccination candidates. Motivation: Presently there are M CT gene families containing a total of 97 gene products and isoforms. Due to the promulgation in sensitivity and specificity of rapid serological immunodetection assays e.g. serial analysis of recombinant cDNA expression libraries (SEREX), the magnitude of novel CT genes and gene families will increase. Hence, characteization of this unique subset of CT genes is fundamental to our erudition of this rapidly emerging novel subset of genes. Obiectives: The sequencing of the human genome provides a useful biological framework for the categoization and systematization of rapidly accumulating biological information. A genomic approach was used to ascertain the locations of the CT genes in the human genome and determine if the genomic locations of the CT genes is nonrandom. An in-silico expression study was conducted for the CT genes with the aim of establishing if CT gene expression is restricted to the testis. A portion of the human genome housing the largest proportion of the CT genes was selected for analysis in order to determine if the surrounding genomic architecture influences CT gene expression. A comparative genomics approach was used in determining if the CT genes are "ancient genes.
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    Hackathons as a means of accelerating scientific discoveries and knowledge transfer
    (Cold Spring Harbor Laboratory Press, 2018) Ghouila, Amel; Siwo, Geoffrey Henry; Entfellner, Jean-Baka Domelevo; Panji, Sumir
    Scientific research plays a key role in the advancement of human knowledge and pursuit of solutions to important societal challenges. Typically, research occurs within specific institutions where data are generated and subsequently analyzed. Although collaborative science bringing together multiple institutions is now common, in such collaborations the analytical processing of the data is often performed by individual researchers within the team, with only limited internal oversight and critical analysis of the workflow prior to publication. Here, we show how hackathons can be a means of enhancing collaborative science by enabling peer review before results of analyses are published by cross-validating the design of studies or underlying data sets and by driving reproducibility of scientific analyses. Traditionally, in data analysis processes, data generators and bioinformaticians are divided and do not collaborate on analyzing the data. Hackathons are a good strategy to build bridges over the traditional divide and are potentially a great agile extension to the more structured collaborations between multiple investigators and institutions.
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    Identification of bacterial pathogenic gene classes subject to diversifying selection
    (University of the Western Cape, 2009) Panji, Sumir; Hide, Winston; Bajic, Vladimir; Faculty of Science
    Availability of genome sequences for numerous bacterial species comprising of different bacterial strains allows elucidation of species and strain specific adaptations that facilitate their survival in widely fluctuating micro-environments and enhance their pathogenic potential. Different bacterial species use different strategies in their pathogenesis and the pathogenic potential of a bacterial species is dependent on its genomic complement of virulence factors. A bacterial virulence factor, within the context of this study, is defined as any endogenous protein product encoded by a gene that aids in the adhesion, invasion, colonization, persistence and pathogenesis of a bacterium within a host. Anecdotal evidence suggests that bacterial virulence genes are undergoing diversifying evolution to counteract the rapid adaptability of its host’s immune defences. Genome sequences of pathogenic bacterial species and strains provide unique opportunities to study the action of diversifying selection operating on different classes of bacterial genes.
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    Taste and odorant receptors of the coelecanth- a gene repertoire in transition
    (Wiley, 2014) Picone, Barbara; Hesse, Uljana; Panji, Sumir; Van Heusden, Peter; Jonas, Mario; Christoffels, Alan
    G-protein coupled chemosensory receptors (GPCR-CRs) aid in the perception of odors and tastes in vertebrates. So far, six GPCR-CR families have been identified that are conserved in most vertebrate species. Phylogenetic analyses indicate differing evolutionary dynamics between teleost fish and tetrapods. The coelacanth Latimeria chalumnae belongs to the lobe-finned fishes, which represent a phylogenetic link between these two groups. We searched the genome of L. chalumnae for GPCR-CRs and found that coelacanth taste receptors are more similar to those in tetrapods than in teleost fish: two coelacanth T1R2s co-segregate with the tetrapod T1R2s that recognize sweet substances, and our phylogenetic analyses indicate that the teleost T1R2s are closer related to T1R1s (umami taste receptors) than to tetrapod T1R2s. Furthermore, coelacanths are the first fish with a large repertoire of bitter taste receptors (58 T2Rs). Considering current knowledge on feeding habits of coelacanths the question arises if perception of bitter taste is the only function of these receptors. Similar to teleost fish, coelacanths have a variety of olfactory receptors (ORs) necessary for perception of water-soluble substances. However, they also have seven genes in the two tetrapod OR subfamilies predicted to recognize airborne molecules. The two coelacanth vomeronasal receptor families are larger than those in teleost fish, and similar to tetrapods, form V1R and V2R monophyletic clades. This may point to an advanced development of the vomeronasal organ as reported for lungfish. Our results show that the intermediate position of Latimeria in the phylogeny is reflected in its GPCR-CR repertoire.